1. No open-ended plots. I *need* specific goals. "Go out and meet people" does not work, and this has been my #1 plot in the last 3 LARPs I've been in. I'm not entirely sure how specific things need to be, but I sure as hell knew who to talk to and what to do for my plot in TMA.
2. Metagame. This needs to be done for 2 specific reasons :
A. Make sure that any players that are relying on you / friends with you actually accomplish what they want. It does not matter how tired / disinterested you are. They need you to work for them to have fun.
B. Sometimes players will play their characters horribly wrong. They will not realize what they are supposed to do / need to do / can do. Even if you have to hit them with a stick, get them to do it. It doesn't matter how nice or mousey your character is supposed to be, get them to do what they have to do. what they are SUPPOSED to do.
3. Don't Metagame. Don't tell the *players* ANYTHING about your character. No matter how irrelevant or how close to the end of the game it may seem, tell them nothing. Don't blather on about it to GMs, AGMs, or spectators. You never know who may be watching. You never know when the person you just told about your clever trap might be playing the person walking into it. *cough* Sami *cough*
4. Stay in-Character. It doesn't matter how bored you are, or how much you want to talk to someone RL. Stay in-character until your characters leave for the night. During Dinner, stay in-character. Invite other characters to dinner. "cover the bill." This brings me to #5.
5. Chit-chat. Come up with a dozen - no - 2 dozen meaningless but pleasant conversation topics for every day of game. There's nothing worse than long protracted sighs of whateverness or elemental conversation .
6. Boredom. If you are bored, ask a GM for suggestions for something to do. Also bring a book (really handy for when your character is unconscious). If you are terminally bored, or people you need to talk to have left for the night, try to stick around a bit, but do go home. If you have no reason to be there other than to be nice to the other players, you might just wonna go home, but please remember #2.
I think that's it. I'm sure I'll have more later.
 Conversation where you say what you mean, not the words one uses to portray it.